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Sunday, September 21, 2008

Logging and the environment- Mitigation- Impact of logging operations- Impact of tree harvesting

The many impacts of logging on the environment can be divided into two broad categories, the timber harvest itself, that is, the removal of trees from the forest, and secondly the impact caused by logging operations such as falling or dragging trees and operation of machinery in the forest.

Impact of tree harvesting

Removal of trees alters species composition, the structure of the forest, and can cause nutrient depletion. This may provide opportunities for some species while creating a loss of opportunity for others. Trees providing midday shade to streams which may alter the stream's temperature either by preventing the sun from shining on the water by day, or by preventing the water from radiating the heat back at night.

In altering the balance of animal and plant species, logging, if not limited to sufficiently small areas, alters the ecological system of the forest. The effect on ecosystems and on biodiversity is the small-scale effect of unrestricted logging.

The large-scale effect of the removal of trees is obviously the impact on the level of carbon in the atmosphere, with its consequences on global climate. Besides the carbon release due to possible burning associated with logging, or possibly with wood processing, the removal of trees prevents carbon from being captured by the trees from the atmosphere. Deforestation, frequently associated with logging, has been assessed to be in fact responsible for 17 percent of annual global carbon a level higher than the one from emissions due to transportation.

Impact of logging operations

Modern ground based logging operations require the use of heavy machinery in the forest. In some areas roads must be built which often causes habitat fragmentation and increased edge effect. The use of heavy machinery in a forest can cause soil compaction. Harvesting on steep slopes can lead to soil erosion, landslides, and water turbidity. Logging on saturated soils can cause ruts and change drainage patterns. Harvest activity near wetlands or vernal pools can degrade the habitat. Forest machines use oils which, if not handled carefully, can cause pollution. Roadbuilding for access to timber in frontier forests often opens up areas previously not accessible, which facilitates further development such as farming.

Mitigation

These problems can be mitigated by using low-impact logging and best management practices, which set standards for reducing erosion from roads. Damage to streams and lakes can be reduced by not harvesting riparian strips. Mitigating the effect of logging can require the full restriction on logging on ecologically important lands, such as forests with a high level of biodiversity. Technological advances in logging equipment can reduce ruts and soil disturbance. Processors and forwarders with caterpillar tracks or other designs to lower ground pressure help to reduce machine impact.